A Dangerous Idea in Zoology: Ignoring the Role of Genetics in Biodiversity Restoration

2017·1.5 MB·English

by  Shelley Burgin

This paper is part of the theme edition of Australian Zoologist - “Dangerous Ideas in Zoology”
A Dangerous Idea in Zoology: Ignoring the
Role of Genetics in Biodiversity Restoration
Shelley Burgin
Faculty of Society and Design, Bond University, Gold Coast, Australia, 4229
Email: [email protected]
The term ‘biodiversity’ emerged in the mid-1980s and quickly became sufficiently popular that it could
have been viewed as a ‘new field of science’. The broader community has also embraced the term
and, ultimately, it has become a proxy for species conservation. As a consequence, conservation of
biodiversity has effectively become the only approach to minimising continued species loss. However,
despite the widespread use of the term, there is confusion over its definition, even among disciplines to
which the term has become a focus. In Australia, much of the biodiversity conservation/restoration is
T
community-driven (e.g., landcare, political pressure of animal welfare groups) with a focus on species and
C habitat biodiversity. Genetic diversity is seldom seriously considered. As a consequence, native species
biodiversity management is often not maximising the potential outcomes. Arguably the greatest issue
A
associated with incorporating genetics more centrally into biodiversity restoration is that its definition
R is often considered complex. In addition, the negative aspects of ignoring the genetic component of
biodiversity may be masked by the positives when the outputs of a program provide many individuals
T
of species considered at risk of extinction despite the longer term outcomes potentially having the
S opposite effect. To better manage biodiversity restoration all of us who use the term within our discipline
B need to ensure that, wherever possible, we seek to inform those around us of the importance of genetic
biodiversity in biodiversity restoration programs. A first step is to determine a simple, all-encompassing
A
definition of biodiversity that explicitly includes genetics.
Key words: definition of biodiversity, single-species management, species diversity, community-driven ecological
restoration, koala conservation, endangered species restoration
DOI: http://dx.doi.org/10.7882/AZ.2014.039
Introduction to ‘biodiversity’

‘Biodiversity’ emerged as a term in the ecological literature is because, in addition to the incorporation of ecological
in the mid-1980s and, within a decade, it had become so attributes within the definition, it also has to be
popular that it could have been viewed as a ‘new field of considered in terms of social goals and values. Using the
science’ (Ghilarov 1996). Subsequently, there has been a United States of America’s (USA) Endangered Species
‘steady increase’ in the use of the term, and particularly Act 1973 as an example, Norton (2006) pointed out that
since the 1992 United Nations Earth Summit Conference social values were central to biodiversity conservation
in Rio de Janeiro (Loreau et al. 2006), evidenced, for in that Act. It actually identifies the ‘social values’
example, in the title of scientific articles (Kaennel 1998; of aesthetics, education, historical, and recreation,
Loreau et al. 2006). However, despite the concept having together with ecological and scientific attributes. As
become entrenched in both the academic and the a consequence, it was suggested that any definition of
general language of the broader community 1, the term biodiversity needed to span both ‘policy discourse’ and
‘biodiversity’ continues to be identified and evaluated ‘biological respectability’. To achieve this outcome, it
differently at all levels of society, internationally and was suggested that a ‘bridge term’ was required that
nationally, and among organisations, local communities, ‘linked discourse about policy goals to scientific data
and even among researchers from different disciplines - and theory, all within a discourse associated with policy
genetics, botany, anthropology, economics (Kaennel 1998; choices’ (Norton 2006, p. 50).
Ewers and Rodrigues 2006; Caillon and Degeorges 2007).
The Australian Environment Protection and
Norton (2006) suggested that defining biodiversity Biodiversity Act 1999 is the Federal Government’s
appropriately was important because of its role as a ‘proxy’ ‘central piece of environmental legislation’. Its emphasis
for species conservation, and because it is effectively the is different in some respects to that of the USA’s
only approach being considered in the minimisation of Endangered Species Act in that the focus of the Federal
continued loss of species. Further, he also suggested that it legislation, and thus the states and territories, provides
was by no means a trivial task to define ‘biodiversity’. This ‘a legal framework to protect and manage nationally
and internationally important flora, fauna, ecological
1 At the end of September, 2014, the key word ‘biodiversity’ on communities and heritage’. If it is assumed that this
‘Google’ elicited 52,000,000 hits, and ‘Google Scholar’ 1,300,000.
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Burgin
reflects Australian community values, the emphasis is such a detailed definition the reader is provided with2 the
on endangered species and ecological communities and benefit of choosing the level of diversity (and presumably
not per se biodiversity. ignoring others) as Wilson says ‘each level can be …
treated independently …’. Most definitions have been
coined in the inventory style of Wilson (Takacs 1996).
‘Defining biodiversity’
Others, such as Wood (2000, p. 41), define biodiversity as
As Norton (2006) acknowledged, the definition of the the ‘sum total of the differences among biological entities’.
word ‘biodiversity’ is complex and, together with others It is not surprising, therefore, that the term has often
(e.g., DeLong 1996; Ewers and Rodrigues 2006; Holt become restricted in common usage to only the most
2006), he suggested that even within the scientific familiar aspect of biodiversity – the species level.
disciplines that embrace biodiversity as a core of their
discipline there was a lack of consensus over the definition The focus of Australian environmental legislation could be
of the term ‘biodiversity’. For example, when Takacs (1996) considered to be within the ‘novelty’ realm of biodiversity
undertook in-depth interviews of what he considered to be definitions, albeit with the emphasis on endangered
the most active of the biological advocates for biodiversity species rather than taxonomic uniqueness. However,
in the world, he asked each of them to define the term. He this definition is not entirely restricted to threatened
reported that the answers differed greatly. This, in part, species conservation per se but also incorporates the
reflected what Wood (2000 p. 41) argued was a major novelty that encompasses ‘endangered ecosystems’ (e.g.,
dichotomy in the definition of the word. He characterised Cumberland Plain Woodlands - DECCW 2011) and,
one of the alternatives in this dichotomy as ‘biological although the human aspects of the USA act that Norton
entities that are different to one another’ and the other (2006) described are not enshrined in the Australian
as the ‘differences among biological entities’. The former environmental legislation, the community tends to drive
emphasised the entities involved while the later focus has restoration decisions, often without a clear understanding
been on ‘an environmental condition or state of affairs of the ecological underpinning required (e.g., Burgin et al.
relative to the entities’. As an example he explained 2005; Saunders 2007).
that using the inventory perspective of his dichotomy,
the emphasis would be focused on the sum total of taxa.
Community driven decision
This would not incorporate any form of weighting where
making in restoration ecology
one species was more valued than another. In contrast,
the alternative form of the definition in this dichotomy Beyond the formal legislative instruments, Australian
favoured taxa that were unique (e.g., a species without governments’ management approach to biodiversity
close relatives). The relative novelty of the taxon would restoration encourages community-driven conservation.
thus have importance under the latter, but not under This is despite, as pointed out above in the comparison
the inventory definition. Takacs (1996, p. 47) found that of the USA and Australian legislative approach, such
others defined biodiversity as ‘the product of organic consideration has not been made explicit in the aims
evolution’. This definition incorporates the ‘diversity of of the legislation. Instead the agenda is often driven by
life in all its manifestations’ and thus emphasises both the political backlash over decisions made that have been
processes and the products of the processes and, although based on ecological information (e.g., koala management,
not necessarily explicit would include genetic biodiversity. Kangaroo Island - Duka and Masters 2005; kangaroo
cull – Australian Capital Territory reserves – Cox and
As the foregoing dialogue indicates, the definition of Thistleton 2012; Jean 2013) or through governments’
biodiversity may appear ambiguous even among the support of community landcare that does not explicitly
professionals that are leaders in the field, and governments. include the need for ecological input (see e.g., Burgin
For example, the definition of Sarkar and Margules 2002; Lunney and Burgin 2002).
(2002), ‘biodiversity is the variety of life’ is typical of
a definition that could either be assumed to simply be Under the banner of ‘Landcare’, there are over 4,000
referring to species level diversity (i.e., the most familiar), Landcare and 2,000 Coastcare groups and ‘many
or applied more broadly and thus encompass, among thousands’ of volunteers (i.e., ‘everyone, everywhere,
other attributes, the genetic biodiversity. However, it is landcare’) in partnerships with governments,
my view that it is a ‘dangerous idea’ not to be at least as communities, and organisations that claimed to care
explicit in defining genetic biodiversity as E.O. Wilson for the ‘natural resources’ of Australia. Their activities
was when he defined biodiversity, albeit restricted to include planting ‘millions of trees’, and restoration of
inventory attributes of biodiversity, as ‘the variety of wildlife habitats (Landcare Australia undated). In an
life across all levels of organization from genic diversity Australian-wide survey of these care groups, 82.5%
within populations, to species, which have to be regarded claimed that their overall aim was to ‘help protect the
as the pivotal unit of classification, to ecosystems. Each
level can be either treated independently or together as 2 The Federal Government’s Environment Protection and Biodiversity
a total picture. And each can be treated either locally Conservation Act, 1999 (Section 17(13) defines biodiversity to include
‘… species, habitats, ecological communities, genes, ecosystem and
or globally’ (Takacs 1996, p. 50). However, even within
ecological processes’ (EPBC 1999).
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This paper is part of the theme edition of Australian Zoologist - “Dangerous Ideas in Zoology”
Ignoring the Role of Genetics in Biodiversity Restoration
local environment for future generations’. However, 2008). However as Kaennel (1998) attested this has
almost half (47.5%) of the groups also claim that their not often been a reality and, as outlined above, is
aim was to ‘educate and inform people about natural definitely not the situation with the term ‘biodiversity’.
resource management’. Despite this, on a scale of 0-5 (5 Currently, this term is being interpreted in different ways
least important), only the need for ‘tools and equipment’ in different contexts to the point where it has become
had a lesser priority (4.27) than either ‘training to build a ‘buzzword’ and thus often misleading rather than
skills and capacity’ (4.17) and information on ‘e.g., informative. Recognising these issues, Kaennel (1998)
best practice, issues, events and government policies’ suggested that, adjudicated by ‘a panel of judges’, more
(4.16). The most common group activity (60.8%) was context-specific specialist terms should be developed for
‘planting and weed management’ (Landcare Australia different attributes of ‘biodiversity’ that are currently
2011). There was, therefore, no evidence that scientific considered to be included in the term, although not
knowledge was viewed as valuable in the support necessarily in any given situation. However, given the
of biodiversity restoration within this network of experience of those who have interviewed leaders in the
volunteers. Based on the data from this Landcare field (e.g., Takacs 1996; Erwers and Rodrigues 2006), I
Australia survey, working within ecological restoration suggest that there is unlikely to be consensus since these
(formally and informally), and my role with the peak scientists only represented the ‘experts’ in the broader
body of catchment management in New South Wales for academic community that consider the term as a part of
over a decade (see e.g., Burgin 2002; Lunney et al. 2002), their vocabulary, and not the broader community.
together with my previous research (e.g., Burgin 2002;
Burgin et al. 2005), there is little doubt in my mind that if With the knowledge that there is no clear definition of
there were a consensus definition of biodiversity among ‘biodiversity’, the obvious question is ‘does it really matter
landcarers it would be heavily focused on ‘community in the restoration of biodiversity?’ I believe that in ecological
biodiversity’, often without what most ecologists would restoration, the development of definitions of biodiversity
view as a clear understanding of the concepts the groups ignoring the concept of genetic biodiversity is a ‘dangerous
seek to incorporate into their restoration activities3. idea’. However, despite an on-going and widespread focus
on biodiversity restoration which is typically focused on
The most broadly disseminated definition of biodiversity species and wildlife habitat (McKay et al. 2005), together
within Australia outside of the research community with an on-going expansion of associated fields of study
would, therefore, be strongly focused on community (e.g., Lindenmayer and Hobbs 2007; Howell et al. 2012;
and species level biodiversity associated with threatened Hobbs et al. 2013), there is limited understanding of the
and endangered species/communities (albeit strongly role of genetics in ecological restoration (Knapp and Dyer
focused on tree planting), with limited concern for the 1998; Jones 2003; McKay et al. 2005).
genetic level diversity or ecosystem services attributes of
biodiversity. For example, Burgin et al. (2005) surveyed In the context of plant communities, T. J. Whittaker
Landcare groups in the Hawkesbury-Nepean Trust Area (1960, 1975) coined the phrase ‘diversity begets diversity’
of New South Wales on the use of local provenance to describe that diverse elements that undergo diverse
(cf. genetic stock) in their planting activities. Of 85 processes will generate higher levels of diversity. The
Landcare groups, 20% were not aware of genetic diversity, alternate is that losses of biodiversity can be expected to
despite having the stated aim of restoring biodiversity. result in further losses.
A substantial number of other groups who claimed they
considered local provenance (genetic biodiversity) in their During reproduction when genes recombine, the
landcare activities, when questioned about the source outcome is the release of genetic and phenotypic
of their seed/seedlings demonstrated that it was not a variability that underpins adaptive change (Lewontin
priority. All indications were that genetic diversity was and Birch 1966; Arnold 2006; Arnold and Martin 2010).
generally not an important consideration and certainly It follows therefore, that lower genetic diversity within
not an overarching one. This widespread lack of concern a population will result in less opportunity for such
for genetic biodiversity can be traced to a lack of variability and thus enhance levels of inbreeding (i.e.,
acknowledgement in definitions of the need and/or value inbreeding depression, lowered heterozygosity/greater
of its consideration in biodiversity restoration. homozygosity). Such outcomes present a higher risk of
local species’ extinction, particularly where habitats are
isolated and/or fragmented (Dunham et al. 1997; Fahrig
Biodiversity restoration in the
2002; Újvári et al. 2002). For example, Újvári et al. (2002)
‘Utopian terminology world’
proposed that low genetic diversity, a result of inbreeding
In the ‘utopian terminological world’ a term and the depression, was a major cause for the endangerment of
associated concept would be substantiated (Kaennel Hungarian populations of the Hungarian meadow viper
Vipera ursinii rakosiensis. In Australia, the brush-tailed
3 It should be noted that not all Landcare ‘restoration’ is focused on
biodiversity restoration per se but rather groups may be focused, for rock-wallaby Petrogale penicillata is critically endangered
example, on restoring other degradation problems such as salinity. It in Victoria. Browning et al. (2001) found that each
is, therefore, inappropriate to assume that they are focused only on
of the State’s populations had low genetic variability
restoration of biodiversity.
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within each of its isolated populations, and that each European history this species has undergone dramatic
population carried alleles that were unique to that oscillations in abundance with local extinctions and
specific population. These findings are typical of random range reductions (Reed and Lunney 1990). Houlden et
genetic drift that results from random loss of genetic al. (1996) observed that the pattern of genetic diversity
diversity and associated fixation of a single genotype (or reflected the history of translocations. Although
at least a reduced number of genotypes) within isolated reduced in number post-European settlement, in the
populations. This is a phenomenon that has been northeast of Australia, koalas were considered common
widely observed in small populations (Frankham 1998; when hunting ceased due to the species’ protection
Frankham et al. 2004; Sanders and Bowman 2012). in the 1930s (Barrett 1943), and they have recovered
Such loss of genetic diversity has been demonstrated without large-scale manipulation (Reed and Lunney
to be significantly associated with a reduction in fitness 1990). Conversely, Lewis (1934) considered that they
due to inbreeding (Reed and Frankham 2003). These were extinct in South Australia and near-extinct in
phenomena have been demonstrated to be most marked Victoria when hunting became illegal. This revelation
in small populations (e.g. Újvári et al. 2002; Reed and sparked major restocking programs which included
Frankham 2003), including endangered species (brush- introductions (sometimes multiple introductions) to
tailed rock-wallaby P. penicillata - Browning et al. 2001; islands in Westernport Bay and the Bass Strait. At
northern hairy-nosed wombat Lasiorhinus krefftii - Taylor least on occasions, these populations were founded on
et al. 1994, 1997) and/or in species that have otherwise very few individuals that had already previously been
been subjected to genetic bottleneck/s (Frankham 1986). through genetic bottlenecks. Subsequently, individuals
from the islands were reintroduced to the mainland and
Probably the most widely studied free-living populations in to Kangaroo Island (for documentation of introductions
regard to the bottleneck phenomena are island populations and translocations see Houlden et al. 1996). Genetic
(Frankham 1998). In a comparison of 202 island diversity was found to be higher in northeast Australia
populations with their ‘mainland counterparts’, Frankham than in the southeast, and lowest on Kangaroo Island.
(1998) found that 81.7% of the island populations had These outcomes parallel the history of manipulation
lower heterozygosity (i.e., genetic variability) than their of koala populations across these areas (Houlden et al.
mainland counterparts. Fragmented, isolated, mainland 1996; Lee et al. 2009).
remnant habitats where wildlife have limited (if any)
ability to migrate typically mimic these island habitats. Genetic bottlenecks are not restricted to the introduction
The same impacts may, therefore, occur that have been or translocation of small numbers of individuals per
evidenced in fragmented P. penicillata populations by se. However, the origin and diversity of the genetic
Browning et al. (2001). stock used for translocation may actually extenuate
the number of bottlenecks that the population will
In the context of restoration of biodiversity, any proceed through, and thus loss of heterozygosity. As has
phenomenon which is a consequence of a small ‘founder historically occurred with koalas, translocated individuals
population’, whether the species is native or exotic, have often been sourced from island populations (e.g.,
will result in a genetic bottleneck. In the extreme, a Houlden et al. 1996; Melzer et al. 2000; Phillips 2000;
population may be founded on the basis of a single Lee et al. 2010). For example, Houlden et al. (1996)
inseminated (or pregnant) female, particularly since reported that koalas for translocation had been sourced
sperm storage is an integral part of the reproductive from island populations that were the descendants of a
cycle in many species (Neubaum and Wolfner 1999). few individuals that had originally been introduced to
For example, classified among the ‘top 100 invasive the island from wild populations of the mainland and
species worldwide’ by the International Union for the sometimes even re-translocated to other islands. This has
Conservation of Nature/Species Survival Commission resulted in multiple genetic bottlenecks, and presumable
(IUCN/SSC 2009), Trachemys scripta elegans red-eared loss of genetic diversity in the translocated populations
slider turtle, an introduced species to Australia, may (Houlden et al. 1996; Lee et al. 2010).
produce fertile offspring for up to five years post-
insemination with multiple clutches annually that may An alternative to translocating free-ranging animals,
include more than 20 eggs (Burgin 2006). At least particularly those that have already declined in the
theoretically, a population may, therefore, be based on source population, has been to instigate captive breeding
just one ‘escaped’ pregnant female. This would generally for later release. Historically, these individuals may be
result in an extreme genetic bottleneck. captured from a restricted area of the species’ range (i.e.,
presumably a sub-set of the genetic diversity available
Genetic bottlenecks may also occur due to population across the population) and, on other occasions where a
declines in a species natural habitat, translocation, species was on the brink of extinction (e.g., Tricholimnas
founding effects and/or introductions. Each of these sylvestris Lord Howe Island woodhen - Miller 1985) it
phenomena has occurred with the koala Phascolarctos is, at best, effectively the remaining genetic diversity for
cinereus; however, unlike many other species, they the species. For example, in the case of the Lord Howe
have been well documented for the koala. Over Island woodhen, by 1980, the maximum number of
Australian
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Ignoring the Role of Genetics in Biodiversity Restoration
breeding pairs was 10, all located in remote areas on the under ‘benign captive conditions’. After 50 generations
island’s highest mountain peaks and thus assumed to be fitness was reduced in their small populations as a result
inbreed individuals at each site, and since the species was of inbreeding depression but in large populations there
widespread and common at human contact, presumably was a small increase in heterozygosity due to ‘modest’
a small sub-set of the previous genetic diversity of the genetic adaptation. When these flies were introduced
species. There had been high adult mortality among to ‘wild conditions’ the reproductive fitness of all 23
breeding females between 1978 and 1980 when adult populations declined substantially (64-86%) compared to
deaths exceeded recruitment into the population. In control populations. Release of these individuals to ‘wild
1980 only three healthy pairs of woodhens remained. conditions’ therefore imposed another substantial genetic
Because breeding was reduced to these six individuals, bottleneck on the captive population.
they were used as the basis of the captive breeding
colony to produce individuals for reintroduction into the These are not the only genetic bottlenecks that the
wild. They effectively represented the genetic future of captivity bred populations face. As already alluded to, some
the population and thus from the beginning the genetic individuals will be better adapted to captive conditions than
welfare of the species was compromised (Ballou et al. others, and thus produce proportionately more offspring. In
2010). By 2007, the population of Lord Howe Island addition, Leberg and Firmin (2008) suggested that when
woodhens numbered 200 (DECC 2007). the number of captive individuals is sufficiently large for
release, typically only a small number is released in any
As with the Lord Howe Island woodhen, Leberg and one episode – usually resulting in an additional genetic
Firmin (2008) reported that a ‘common feature’ of captive bottleneck. As Woodworth et al. (2002) observed, different
breeding populations is that they are based on a small individuals released into the wild respond differently.
number of founding individuals. Generations of individuals from the same source stock
will; therefore, likely result in a skewing of the population
This may occur, even when the resources are available to towards some sub-set of the genetic diversity that survived
establish larger breeding populations. An additional issue these multiple bottlenecks. As a consequence genetic
with a small founding population is that the smaller the deterioration in captivity may be a major problem in long-
number of individuals available for captive breeding the term captive breeding programs, and even for the wild
more likely it will be that the matings will be between populations that the captive animals have been released
related individuals. Frequently, the source of such animals into over future generations.
for captive breeding are island populations that typically
have lower genetic diversity than mainland populations Other factors that may influence captive breeding
(e.g., dibbler Parantechinus apicalis – Mills et al. 2004; koala success include disease outbreaks, establishment of
- Houlden et al. 1996; Melzer et al. 2000; Phillips 2000). self-sufficient captive populations, domestication,
maintaining administrative continuity, and the
Captive populations are also exposed to additional genetic substantial costs of the operation (Snyder et al. 1996).
bottlenecks because not all genotypes are successful In addition to the issues of poor success rates due
under captive conditions. Under such circumstances, to reintroductions (Snyder et al. 1996; Woodworth
inbreeding depression will result in a reduction in mean 2002), Snyder et al. (1996) also voiced concern that
population fitness and expose the population to the threat captive breeding was becoming increasingly popular,
of reduced viability. This problem is increasingly an issue and thus may pre-empt alternative recovery techniques.
as the number of founders is reduced (Frankham 1995a; They considered that captive breeding should not be
Hedrick and Kalinowski 2000; Spielman et al. 2004). One ‘invoked prematurely’ and such programs should not
reason for this is that inbreeding exposes selection to be introduced to recovery programs before appropriate
the deleterious, recessive genetic characteristics that the evaluation of all alternatives, and before it had been
population carries. This process, referred to as purging, determined that captive breeding was necessary for the
reduces the frequency of deleterious genes within the survival of the species. It was recommended that captive
population and thus may also reduce inbreeding depression breeding should be introduced only as a ‘last resort’ in a
(Crnokrak and Barrett 2002; Glémin 2003; Leberg and species recovery plan after all other effective, short term
Firmin 2008). However, while recognising the role that options were exhausted.
inbreeding depression has on the expression of deleterious
genes in a population, Frankham (1995b) suggested that Such a situation has apparently occurred with the two
the negative effects of purging in small populations have Australian species of corroboree frog (Pseudophryne
been overestimated. No matter what the outcome, an corroboree, Pseudophryne pengilleyi). Until 1966 both
inbred population is subjected to a genetic bottleneck species were considered abundant (Colefax 1956;
at this stage of the captive breeding cycle with further Pengilley 1966) but both species have subsequently
genetic bottlenecks due to, for example, release from declined, and by 2008 it was predicted that the two
captivity into the wild. These effects were observed by species where critically endangered and could be extinct
Woodworth et al. (2002). They investigated populations of in the wild in three years (Morgan et al. 2008). In 2013
Drosophila sp. of different densities that were maintained no corroboree frogs were found during the annual census.
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The major cause of the decline coincided with the chytrid Canis lupus bred in Scandinavian zoos presented with the
fungus Batrachochytrium dendrobatidis and the decline of effects of inbreeding that included a reduction in juvenile
other species within the Southern Alps (Hunter 2007, weight, low reproduction, reduced longevity, and blindness.
Hunter et al. 2009). Genetic analysis across the range The varying traits observed were linked to genes originating
of both species indicated that heterozygosity in the from different founding pairs, and it was predicted that such
remnant wild populations remained high (Morgan et al. traits would affect fitness within the population.
2008). Captive breeding/husbandry was introduced for
the species. Eggs of the northern corroboree frog have As indicated above, one of Witzenberger and Hochkirch
been collected and reared in captivity to mature frogs (2011) findings was that population fitness was improved
and ultimately they will be released to the wild. It is also when new founders were successively integrated into
planned to maintain a ‘self-sustaining (breeding) captive captive breeding populations. Spielman and Frankham
population’ as insurance against the ultimate extinction (1992) provided evidence that even one immigrant
of both of these species in the wild (ESDD 2014). into a small isolated captive population of Drosophila
Taronga Zoo (Sydney) introduced a breeding program melanogaster approximately doubled the reproductive
for the southern corroboree frog with ultimate release of fitness of the population.
offspring to the wild. In 2013 the program was extended
to trial the release of eggs and tadpoles into enclosures It is not necessarily the captive breeding environment
within the species’ range (TCSA 2013). If successful, per se that creates genetic bottlenecks in biodiversity
this will potentially reduce some of the bottleneck effects restoration. The factors outlined above that may impact
due to captive breeding although not all of them. In the on captive populations, may also occur in free-living,
face of on-going decline and critical endangerment of isolated populations including island or isolated and/
these species, caused (at least in part) by disease (Hunter or fragmented mainland sites (e.g., dibbler Parantechinus
2007; Hunter et al. 2009), there is presumably no other apicalis - Mills et al. 2004; koala - Houlden et al. 1996;
apparent avenue to immediately overcome the ultimate black-footed rock-wallaby Petrogale lateralis – Eldridge
extinction of the species. Captive breeding would thus, et al. 1999; brush-tailed rock-wallaby - Browning et al.
presumably, have been an example of the ‘last resort’ 2001, Taggart and Houlden et al. 2001; northern hairy-
that Snyder et al. (1996) identified. The captive breeding nosed wombat – Taylor et al. 1994, 1997). For example,
of the Lord Howe Island woodhen was another such Eldridge et al. (1999) observed that island populations of
example since the population was effectively functionally the black-footed rock-wallaby suffered from inbreeding
extinct with the few remaining adults being lost at a depression that included reduced fecundity in females,
faster rate than replacement (Miller 1985). a skewed sex ratio, and increased levels of fluctuating
asymmetry. Seymour et al. (2001) also observed the effects
Witzenberger and Hochkirch (2011) surveyed the of inbreeding suppression in free-ranging koalas that
literature that focused on the molecular genetics of captive had been through sequential founding events in recent
breeding of endangered animal species. The majority of history. The incidence of testicular aplasia was positively
the studies (70%) reported on specific breeding programs, correlated with effective inbreeding coefficients derived
and these showed a ‘marked bias’ to a few species. The from heterozygosity values, and was undetected in a non-
most studied were carnivores (25%), ungulates (26%), bottlenecked population they studied.
birds (19%), primates (9%), and reptiles (9%). The
authors concluded that the genetic impacts of captive As other researchers had previously reported (e.g.,
breeding varied substantially due to a range of factors. Franklin 1980; Lande 1995; Woodworth et al. 2002),
Overall; however, there was a strong correlation between Witzenberger and Hochkirch (2011) recommended
genetic diversity, size of founder population, and the size of that when the goal for captive breeding colonies is to
the captive population. It was concluded that to minimise retain evolutionary potential (as should be the situation
inbreeding there should be a minimum of 15 individuals in biodiversity restoration programs), the population
in the founder population, and at least 100 in the captive size should be substantially larger than the 100 that
population. Individuals in the founder population should they recommended as the minimum size. However,
also not be related, and new founders should be integrated even among the ex situ populations managed by the
into the population successively. Associations of Zoos and Aquariums, Baker (2007)
reported that 67% had a population size of less than that
While effective population size in a breeding colony is which Witzenberger and Hochkirch (2011) identified as
clearly of importance, the identity and number of founders being the minimum number required in most situations
(i.e., genetic makeup) that contribute to the captive that they investigated – some required larger population
breeding program also has a major determining effect sizes. As previously indicated, small founder populations
on the genetic diversity (Witzenberger and Hochkirch and/or effective population size may exacerbate the issues
2011). For example, Laikre and Ryman (1991) found associated with inbreeding. For example, it was suggested
that although it was previously reported that mammalian by Ralls and Ballou (1986) that such populations are
carnivores and other species with similar social structures ‘likely’ to become extinct due to chance events including
were adapted to close inbreeding, they found that the wolf a succession of births of one sex, disease, and/or genetic
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400 Zoologist volume 38 (3) 2017
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Ignoring the Role of Genetics in Biodiversity Restoration
problems. For example, they reported that across 45 are often referred to as ‘flagship species’, although the
mammalian populations (8 orders, 37 genera), juvenile term may also incorporate any of the popular, charismatic
mortality of inbred young was higher than non-inbred species, and Leader-Williams and Dublin (2000) noted
young in over 90% of populations. that the terms were often used interchangeably.
As previously identified, sequential bottlenecks occur The term ‘flagship’, and by association, other such terms
within captive breeding populations. Over time these may indicating ‘iconic’ status for a species was apparently first
result in changes in behavioural and physiological traits used by conservationists in the mid-1980s (Mittermeier
that have allowed specific lineages to prosper in captive 1988; Western 1987; Leader-Williams and Dublin 2000)
breeding conditions but, in turn, prove detrimental in to raise awareness for the conservation of the golden lion
natural situations. This is because the two environments tamarin Leontopithecus rosalia in Brazil. The conservation
are very likely ‘radically’ different. In this context, of this species did play the broader role of conservation of
Lynch and O’Hely (2001) suggested that managers of an biodiversity, presumably because their conservation was
endangered species population face ‘double-jeopardy’. inexplicitly linked to their rainforest habitat (Mittermeier
Failure to intervene when confronted with species 1988; Dietz et al. 1994; Mittermeier et al. 2005).
decline may result in the species’ extinction. Conversely,
genetic changes in the captive environment may reduce No matter which of the numerous terms are used to
the potential for these same individuals to cope under identify iconic species (cf. Leader-Williams 2000), they are
natural conditions since captive bred populations may considered to be symbols or ‘rallying points to stimulate
‘rapidly undergo significant evolutionary change’ in their conservation awareness and action’ and financially support
morphological, behavioural, and physical makeup that conservation of the associated species’ habitat and thus,
may have a negative impact on fitness under natural indirectly, support biodiversity conservation within the
conditions (Arnold 1995; Lynch and O’Hely 2001; Araki species’ range. For example, primates have been considered
et al. 2009). In such situations, there may be a ‘carry- the best flagship species for entire regions (Mittermeier
over effect’ of the captive breeding into the wild that 1988; Dietz et al. 1994; Mittermeier et al. 2005).
has the potential to reduce reproductive fitness within
the offspring of free-ranging species, including that of In the words of Duka and Masters (2005 p. 172), the koala
subsequent generations. Araki et al. (2009) observed this has a ‘high and favourable social profile and appeals to a
phenomenon in steel-head trout Oncorhynchus mykiss. wide variety of people, particularly overseas visitors’, and it
Overall relative reproductive fitness in wild-born fish has frequently been described as a ‘flagship’ species (Penn
from captive-bred parents was 37% while those from one et al. 2000; Barua et al. 2011; Cristescu 2011) and/or as
captive-bred parent and one wild-bred parent was 87% ‘charismatic megafauna’ (Feldhamer et al. 2002; Barney et
of that of offspring from two wild-bred parents. al. 2005; Tisdell and Nantha 2007). Arguably the species
has gained this iconic status in recent decades due largely
A factor that directly affects the viability of captive-bred to vocal and emotional community outpourings that have
individuals that are released into the wild is their chance driven species and ecosystem management of the species,
of survival. After an extensive review of the literature, despite contrary scientific advice (Jackson 2007; Melzer
Jule et al. (2008) concluded that survivorship success in 2009). However, not all native species are afforded the
captive-bred carnivores compared to individuals born same level of concern. For example, both the western grey
in the wild and translocated varied. Across five families kangaroo Macropus fuliginosus (Cheal 1986; Arnold et al.
and 17 species of captive-bred carnivores, significantly 1989; Duka and Masters 2005) and the tammar wallaby
fewer were likely to survive in the wild than wild- Macropus eugenii (Wright and Scott 1999; Chambers and
born individuals. Captive-bred individuals were more Bencini 2000) are culled, and kangaroo harvesting (i.e.,
susceptible to starvation, unsuccessful predator and/or culling) is considered a successful management option
competitor avoidance, and disease, although over 50% (e.g., Caughley et al. 1987; Arnold 1988; Grigg 1988,
of all fatalities were directly caused by humans. 1995), although the program has had detractors (e.g.,
Arnold 1988; Stacker 1988; Hale 2004).
Biodiversity restoration or
In contrast to the lack of successful intervention in
community driven single-species
macropod culling on Kangaroo Island (Wright and Scott
management of favoured species? 1999), the decision to cull koalas on the Island because of
their ‘pest status’ in late 1970s (Masters et al. 2004), met
Throughout this paper, I have written of ‘single-species with ‘strong adverse reaction’. Although no surveys were
management’ (cf. Simberloff 1998). All of the Australian undertaken of community attitudes, based on unsolicited
species mentioned would fall under the definition of feedback to governments, the koala management program
one or more of the widely used terms – ‘charismatic was restricted to sterilisation and translocation (Duka
megafauna’ and ‘flagship’ species (see e.g., Leader-Williams and Masters 2005), although humane culling of tammar
and Dublin 2000). For example, the koala would definitely wallabies was being undertaken on the Island at the time
be considered ‘charismatic megafauna’, while mammals without vocal resistance (Wright and Scott 1999).
Australian
2017 Zoologist volume 38 (3) 401
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When the koala management program commenced in efforts are based on captive breeding or the management of
1997, the founder population of 18 koalas translocated populations within the wild. It is not that the importance
to Kangaroo Island between 1923 and 1925 was of genetic biodiversity is unknown. Rather it is considered
estimated to be 5,000 although this was later deemed complex, is typically unobservable, and often not explicitly
to be a substantial underestimate. Some years after acknowledged in biodiversity restoration, even when the
implementation of the management regime, when fundamental principles are carefully incorporated.
surveys were undertaken in 2000-2001, the original
estimates were confirmed to be erroneous. As a While those who work, teach and/or undertake research
result, the estimate of koalas was revised upwards to within the area of biodiversity do not emphasise
approximately 27,000. There were also no scientific its importance, even within definitions of the word
controls implemented at the beginning of the program ‘biodiversity’, it is logical that policy makers and the
and thus interpretation of the results of the program broader community will not acknowledge its importance
has been problematic (Maters et al. 2004). These or even be aware of it. For example, the Lord Howe
shortcomings provide an indication of the extent to Island woodhen went from the brink of extinction to
which political pressure, rather than scientific method, 200 birds in a captive breeding program between 1980
prevailed in this program. Duka and Masters (2005) and 2007 (DECC 2007). However, I suggest that in
reported that they agreed with criticism of the program terms of genetic biodiversity it would have been a much
for such reasons. They also considered that the program more modest gain, and probably none. Likewise a trip
was expensive, and did not address the longer term to Taronga Zoo provides the visitor with exposure to
management of the species. Clearly, the program will information on the thousands of corroboree frogs bred
not satisfy either the management of koalas, or the at the zoo. Based on the published surveys of the genetic
restoration of biodiversity including genetic biodiversity diversity of the species, and because the breeding is
on the island. The role of ‘flagship’ has; therefore, failed being undertaken under the auspices of the Zoo who
both the species and the biodiversity of the Island have well developed breeding programs for a range of
more generally. Resources spent on the program could species, it could be assumed that the best science has
have been better diverted to more lasting biodiversity been incorporated into this program. However, what
restoration outcomes. would capture most visitors’ attention is the large
number of iconic frogs that have been bred. However,
In other ways, koalas have not proved to be a great what is not observed are the issues, some outlined
‘flagship’ species for biodiversity restoration. For example, above, which potentially accompany captive breeding.
in fragmented agricultural landscapes, koalas were found Few people who visit Taronga Zoo without knowledge
to spend more of their time in four to seven year old of the genetic pitfalls of captive breeding, but engage
eucalypt plantations than in adjacent natural areas, with the corroboree frog exhibit, would leave without
presumably because of a ready supply of eucalypt leaves having a positive view of the program. Many probably
- food which is not typically included in the diet of other would leave viewing the concept of captive breeding
native arboreal marsupials of the area. Koalas also do not as an appropriate approach to biodiversity restoration.
require diurnal shelter and breeding sites in tree hollows Some may even become advocates for captive breeding.
that most species of the native arboreal marsupials This is not surprising since it is an impressive program
require (Kavanagh and Stanton 2012). Focusing on and the species is viewed as endangered and iconic.
managing for the ‘flagship’ koala in the study area is,
therefore, unlikely to have beneficial outcomes for the As a consequence of being convinced of the success
local biodiversity more generally. Indeed, the logical of such biodiversity restoration projects, governments
outcome of the research based narrowly on the findings may bow to pressure from the community, and even
of the needs of the flagship species (i.e. koala) would offer substantial resources for biodiversity restoration
logically be to expand the eucalypt plantations. that may, in the extreme, have no real benefit for
the targeted species and maybe even a detrimental
effect on the species over the longer term. Indeed, it
Conclusions
may also be at the expense of other, more appropriate
The approach to native biodiversity restoration, as currently approaches to biodiversity restoration for populations
managed, is not maximising the potential outcomes that of the same species and/or for other species that may
could be achieved over the longer term. A fundamental be evolutionarily more important, but are bypassed
issue is the lack of a clear understanding of the word due to lack of resources. As a consequence biodiversity
‘biodiversity’. There is a need to recognise the centrality continues to unnecessarily erode. For example, due
of genetic biodiversity within the definition of biodiversity to public pressure, although without a quantitative
and thus in the management of species. In the longer assessment of opposition or even a comprehensive
term, any ‘successful’ restoration program that ignores the assessment of the number of koalas on the Island,
importance of genetic biodiversity will be largely due to individuals of an inbred population on Kangaroo
chance. This will be the situation, whether the restoration Island were sterilised and released/translocated. The
Australian
402 Zoologist volume 38 (3) 2017
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Ignoring the Role of Genetics in Biodiversity Restoration
program, as devised, could not address the real issue nothing has been achieved in terms of even the long-
over the longer term – the super-abundance of koalas term management of the koala.
on the Island, or the associated damage that they were
having on their food species, and thus the Island’s Arguably the greatest issue associated with incorporating
flora and fauna that were being affected by their genetics more centrally into biodiversity restoration is
super-abundance. However, instead of addressing these that the definition of biodiversity is often considered to
issues, the funds were effectively wasted and thus the be complex, whereas the negative aspects of biodiversity
habitat of other native species on Kangaroo Island restoration may appear to be positive when the outputs
continued to be degraded by the genetically depurate introduce a species or boost numbers of a species that
superabundant population of koalas. has been deemed to be at risk of extinction despite the
longer term outcomes potentially having the opposite
This was typical of a situation where scientific effect. I suggest that the way forward is for all those of
knowledge has been over-ruled to ‘save’ the ‘charismatic us who encompass biodiversity restoration within our
iconic’/‘flagship’ species. However, although species discipline areas to redouble our efforts to ensure that,
such as koalas are touted as the saviour of biodiversity, wherever possible, we seek to inform those around us
in the sense of the long-term management of the of the importance of genetic biodiversity. In doing so, it
ecological diversity of Kangaroo Island, it was because would be useful if we could make it a matter of priority
it was an iconic species that the koala has had to develop a simple, all-encompassing definition of
effectively the opposite effect. Rather than its presence biodiversity that explicitly includes genetics along with
supporting biodiversity restoration of Kangaroo Island, the other levels of diversity.
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